Playback system for an optical disc presenting a character or a graphic pattern formed by specified pit patterns on data tracks

ABSTRACT

A CD-ROM is provided with an area for forming a character/graphic pattern. The character/graphic pattern is formed in such a way that data, which generate on the CD-ROM two sorts of pit patterns having average reflectances different from each other to a perceptible extent, are respectively recorded inside and outside the character/graphic pattern. Unless an illegal copy disc is produced by duplicating the legal original disc of the CD-ROM at a very high precision, the character/graphic pattern of the copy disc is invisibly deformed by the discrepancy between the arrangements of the pit patterns of the copy disc and the original disc.

This application is a continuation of application Ser. No. 08/301,889,filed Sep. 7, 1994 now U.S. Pat. No. 5,608,717.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to information recording media, such as anoptical disc or an optical card, on which information are recorded inaccordance with optical features. More particularly, it relates totechniques for inhibiting the illegal duplications of the informationrecording media.

2. Description of the Related Art

A CD-ROM (compact disc read only memory), which is a kind of opticaldisc, can be mentioned as a typical example of information recordingmedia on which information are recorded by affording optical featuresthereto.

Many types of CD-ROM adopt the CLV (constant linear velocity) system inwhich data are recorded using pits of regular intervals. This CLV systemcan make the data capacity of the CD-ROM larger than the CAV (constantangular velocity) system in which data are recorded using pits ofintervals determined in accordance with the radial positions of theCD-ROM so that angles with respect to the center thereof may be heldconstant at all times. Besides, in the CD-ROM's, frames are set asrecord units irrespective of the CLV system and the CAV system. Asillustrated in FIG. 18 of the accompanying drawings, each frame 1 iscomposed of data of fixed length, and a sync signal 2 affixed to thehead of the data.

Incidentally, it is also possible that the CLV system and the CAV systemcoexist on one optical disc.

By way of example, according to a technique disclosed in the officialgazette of Japanese Utility Model Registration Application Publication(KOKOKU) No. 44927/1993, an optical disc is provided with a record areabased on the CLV system and a record area based on the CAV system, andstill picture data, etc. are recorded in the latter record area. Inaddition, according to a technique disclosed in the official gazette ofJapanese Patent Application Publication (KOKOKU) No. 33470/1993, anoptical disc is provided with a record area based on the CLV system anda record area based on the CAV system, and the positions of therespective record areas are separately recorded as address information.The address information are utilized for the change-over between therotational controls of a disc motor for the record area based on the CLVsystem and the record area based on the CAV system.

In this specification, an "original disc (original version)" is intendedto mean a CD-ROM which is lawfully produced from a "legal master disc(legal master version)". On the other hand, a "copy disc (copy version)"is intended to mean a CD-ROM which is unlawfully produced from an"illegal master disc (illegal master version)" that is, in turn,prepared from the original disc.

At present, CD-ROM's are extensively utilized for recording digital datasuch as various sorts of software, document data and image data.

Such digital data which are recorded on the CD-ROM's are usually underthe protection of copyrights. Nevertheless, the production and sale ofillegal copy discs of the CD-ROM's have heretofore recurred.

Especially in the fields of software for games and electronicpublications including independent volumes, dictionaries etc., theproduction of the illegal copy discs has often been organically made andhas formed a factor for hampering normal commercial transactions.

The above mentioned copy discs of the optical disc such as CD-ROM can beproduced from the illegal master disc thereof. This illegal master discof the copy discs is prepared from a mold in which the shapes of pitarrays recorded in the information recording surface of the originaldisc of the optical disc are transferred by the use of a plasticsmaterial or the like. The molding technique, however, often fails toexactly produce the copy discs for the reason that the shapes of the pitarrays need to be transferred after the protective film of the originaldisc is removed to expose the pit array surface, so the arrayed pits aredeformed at the stage of removing the protective film. Especially in acase where the protective film is rigid, the production of the copydiscs of the optical disc is very difficult.

Therefore, the illegal master disc of the copy discs of the optical discis ordinarily prepared using data read out of the original disc of theoptical disc, just as in the case of producing the original disc fromthe legal master disc of the optical disc.

Meanwhile, in order to prevent a pirate from producing such copy discsof the optical disc, a copyright has heretofore been indicated on thefront surface of the original disc of the optical disc by carving orprinting characters, a graphic or the like.

In addition, examples to be mentioned below have been known as prior-arttechniques for discriminating the illegal copy disc of the optical discfrom the legal original disc thereof.

The technique disclosed in the official gazette of Japanese PatentApplication Laid-open No. 286768/1992 utilizes the fact that the syncsignal 2 stated before with reference to FIG. 18 cannot usually be readout as data. With this technique, another signal is substituted for partof the sync signal 2 and is recorded beforehand. In playing back anoptical disc, the presence or absence of the substitute signal isespecially detected, and the optical disc is decided as an illegal copydisc in the absence of the substitute signal.

In the official gazette of Japanese Utility Model RegistrationApplication Laid-open No. 20884/1990, it is disclosed to form a visiblepattern on the front surface of the signal recording layer of an opticaldisc. Also, it is disclosed in the official gazette of Japanese PatentApplication Laid-open No. 179941/1990 that a pattern or the like whichis visible is formed by changing the pit shapes of the signal surface ofan optical disc.

Regarding the technique disclosed in the official gazette of JapanesePatent Application Laid-open No. 286768/1992, the sync signal 2including the substitute signal can be, in itself, reproduced.Therefore, it is not very difficult to produce an illegal copy disc ofthe optical disc in which the sync signal 2 including the substitutesignal is stored.

On the other hand, according to the technique disclosed in the officialgazette of Japanese Utility Model Registration Application Laid-open No.20884/1990 or Japanese Patent Application Laid-open No. 179941/1990, thestep of forming characters, a graphic or the like needs to be separatelyperformed in addition to a conventional process for preparing the masterdisc of the optical disc.

SUMMARY OF THE INVENTION

The present invention has for its object to offer an informationrecording medium whose master disc can be prepared by a process similarto the conventional one, and which is formed with a visible pattern thatis very difficult to reproduce on the copy disc of the informationrecording medium.

Another object of the present invention is to offer a playback systemwhich can refuse the utilization of an illegal information recordingmedium produced by duplicating a legal information recording medium.

In one aspect of performance of the present invention for accomplishingthe first object, an information recording medium, such as an opticaldisc, which has a record surface, and which records information in termsof pit patterns formed on a plurality of tracks of the record surfaceand corresponding to data to-be-recorded; comprises:

at least one area which is provided on the record surface, and in whicha specified pit pattern corresponding to either of specified data or aspecified data pattern is concentratedly formed in order that either ofa character pattern or a graphic pattern having a size which is visibleon the basis of a difference between light reflectances may be presentedin a pattern displaying area provided on the record surface;

an average light reflectance of the specified pit pattern differing froman average optical reflectance of surroundings of the at least one areato a visually perceptible extent.

In another aspect of performance of the present invention foraccomplishing the second object, in the case where such an informationrecording medium is the optical disc, a playback system for playing backthe optical disc comprises a memory for storing therein positionalinformation which specifies a position of the pattern displaying area ofthe optical disc; reproduction means for reproducing the data recordedon the mounted optical disc; control means for reproducing the data fromeither of the area or the areas of the record surface of the mountedoptical disc through the reproduction means, the either of said area orthe areas being specified by the positional information stored in thememory; and reproduction inhibition means for suspending subsequentplayback of the mounted optical disc on condition that the reproductionof the data from the either of the area or the areas as specified by thepositional information has failed.

In accordance with the information recording medium of the presentinvention as mentioned above, the specified pit pattern corresponding toeither the specified data or the specified data pattern isconcentratedly formed, whereby the visible character/graphic pattern isexpressed on this information recording medium.

When the illegal copy disc of the information recording medium isproduced by duplicating the data, the arrangement of such a pit patterndeviates due to a precisional problem. Moreover, it is very difficult toconfine the deviation to the extent that the character/graphic patternshaped by the arrangement of the pit pattern is not greatly deformed. Itis accordingly very difficult for the character/graphic pattern existingon the legal original disc of the information recording medium to besimilarly duplicated on the illegal copy disc.

Besides, in accordance with the playback system of the present inventionas mentioned above, the data is reproduced from the area of the mountedoptical disc containing the character/graphic pattern, and thesubsequent playback of the mounted optical disc is suspended oncondition that the reproduction of the data has ended in failure.Therefore, even when the character/graphic pattern has been formed on anoptical disc by any expedient other than the data duplication, theoptical disc cannot be played back and utilized. That is, such anillegal copy disc has its utilization refused in the playback systemaccording to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the external appearance of a CD-ROM in thefirst embodiment of the present invention;

FIG. 2 is a fragmentary view showing the shape of a pit pattern which isborne on the CD-ROM of the first embodiment;

FIG. 3 is a diagram for explaining the pit patterns of the CD-ROM of thefirst embodiment;

FIGS. 4A and 4B are diagrams for explaining those deviations of pitswhich occur in the case of duplicating the CD-ROM of the firstembodiment;

FIG. 5 is a graph showing the relationship between the radial trackposition and the linear velocity of a CD-ROM in the second embodiment ofthe present invention;

FIGS. 6A, 6B and 6C are diagrams each showing the layout and storagesystem of character/graphic pattern areas which are formed in a CD-ROMin the third embodiment of the present invention;

FIG. 7 is a graph showing the relationship between the radial trackposition and the linear velocity of the CD-ROM of the third embodimentas depicted in FIG. 6B;

FIG. 8 is a graph showing the relationship between the radial trackposition and the linear velocity of the CD-ROM of the third embodimentas depicted in FIG. 6C;

FIGS. 9A thru 9C are diagrams for explaining the arrangement of acharacter/graphic pattern area and a specular portion which are formedin a CD-ROM in the fourth embodiment of the present invention;

FIG. 10 is a block diagram showing the circuit arrangement of a playbacksystem in the fifth embodiment of the present invention;

FIG. 11 is a block diagram showing the circuit arrangement of therotating servo loop of a servo circuit which is included in the playbacksystem of the fifth embodiment;

FIG. 12 is a flow chart showing the steps of a process which is executedby a CD-ROM controller included in the playback system of the fifthembodiment;

FIG. 13 is a flow chart showing the steps of another process which isexecuted by the CD-ROM controller included in the playback system of thefifth embodiment;

FIG. 14 is a flow chart showing the steps of a process which is executedby a CD-ROM controller included in a playback system in the sixthembodiment of the present invention;

FIG. 15 is a flow chart showing the steps of a process which is executedby a CD-ROM controller included in a playback system in the seventhembodiment of the present invention;

FIG. 16 is a diagram showing an example of that featuring part of acharacter/graphic pattern which is used for collation by the CD-ROMcontroller included in the playback system in the seventh embodiment;

FIGS. 17A thru 17D are schematic perspective views each showing therecord/playback system of an optical memory card; and

FIG. 18 is a diagram showing frames which are recorded on a CD-ROM.

PREFERRED EMBODIMENTS OF THE INVENTION

Embodiments of an information recording medium and a playback system forthe playback thereof according to the present invention will bedescribed below by taking as an example a case where the informationrecording medium is a CD-ROM which is a kind of optical disc.

Now, the first embodiment of the present invention will be described.

FIG. 1 illustrates the signal surface of a CD-ROM in this embodiment.

In this embodiment, the signal surface of the CD-ROM 4 is provided witha character/graphic pattern 14 which is visible, that is, which can beseen with the naked eye. Herein, the character/graphic pattern 14 shallexpress the content of the copyright of data or a program stored in theCD-ROM 4, the trademark of the data stored in the CD-ROM 4 or that ofthe CD-ROM 4 itself, or the content of any other right concerning thedata stored in the CD-ROM 4 or the CD-ROM 4 itself. Of course, thecharacter/graphic pattern 14 may well express any other item.

How the character/graphic pattern 14 is formed, will be elucidatedbelow.

First, how to record data on the signal surface of the CD-ROM 4 will beexplained.

By way of example, the data are modulated by the EFM (eight-to-fourteenmodulation) system which is applied to a CD for musical use, and themodulated data are recorded in the signal surface of the CD-ROM 4 by theCLV system.

More specifically, data, each being composed of 8 bits! as listed in theleft column of Table 1 below, are respectively converted into EFMchannel bit patterns each being composed of 14 bits! as listed in theright column of the table. Further, channel bit patterns of 17 bits! arerespectively generated by adding margin bits of 3 bits! to each of theEFM channel bit patterns of 14 bits!, and each of them is recorded asone unit on the CD-ROM 4.

                  TABLE 1                                                         ______________________________________                                        Data    EFM Channel Bit Pattern                                               ______________________________________                                        000     01001000100000                                                        001     10000100000000                                                        002     10010000100000                                                        .                                                                             .                                                                             088     01001000000100                                                        089     10000000000100      11T Pattern                                       090     10010000000100                                                        .                                                                             .                                                                             .                                                                             167     00100100001001                                                        168     01001001001001      3T Pattetn                                        169     10000001001001                                                        .                                                                             .                                                                             .                                                                             255     00100000010010                                                        ______________________________________                                    

Subsequently, a master disc is prepared. The signal surface of theCD-ROM 4 is formed by the master disc with the patterns of microscopicprotrusions (pits) of predetermined width and height as shown in FIG. 2,the pit patterns being determined in accordance with the values of thechannel bit patterns. The preparation of the master disc is carried outin such a way that, while being rotated by a disc motor (a spindlemotor), the master disc is formed with pit patterns therefor ontracks-to-be-formed by a laser. Incidentally, the pits are sometimesmicroscopic recesses of predetermined width and depth.

On this occasion, the data "1" of the channel bit pattern corresponds tothe edge of each pit. By way of example, the 8-bit data "168" indicatedin Table 1 is converted into the EFM channel bit pattern"01001001001001", in which the data "1" appears every third bit.Accordingly, when letter T is let denote a pit length corresponding toone channel bit, the pit pattern corresponding to the 8-bit data "168"includes two pits 301 each of which is 3T long and which are spaced 3Tfrom each other.

Likewise, the pit pattern corresponding to the data "89" includes a pitwhich is 11T long. By the way, in the case of the EFM system indicatedin Table 1, the smallest pit length becomes 3T, and the greatest pitlength becomes 11T.

Subsequently, the pit patterns are transferred from the prepared masterdisc onto the signal surface of the CD-ROM 4. Further, a lightreflection film such as aluminum thin film is deposited by vacuumevaporation onto the whole signal surface of the CD-ROM 4 formed withthe pits, and a transparent protective layer is formed thereon.

In the CD-ROM 4 thus produced, the reflectances of the pit portions andnon-pit portions (land portions) thereof for light are different. In theplayback operation of the CD-ROM 4, therefore, the channel bits arereproduced to read the data owing to the changes of the lightreflectances.

Meanwhile, in this embodiment, the visible character/graphic pattern 14is formed on a part of the signal surface of the CD-ROM 4 by utilizingthe difference of the reflectances of the pit portions and the non-pitportions.

More specifically, owing to the difference of the reflectances of thepit portions and the non-pit portions, average reflectances for lightbecome different between a certain pit pattern and a different pitpattern. Therefore, such certain pit patterns are concentrated orcrowded in the shape of the desired character/graphic pattern 14, andsuch different pit patterns are arranged outside the character/graphicpattern 14.

This embodiment utilizes the pit patterns corresponding to the 8-bitdata "168" stated before, and the pit patterns corresponding to the8-bit data "89".

FIG. 3 is a diagram in which a part of the character/graphic pattern 14borne on the signal surface of the CD-ROM 4 is enlarged and depicted.Here, the data constitutes one frame conjointly with a synchronizingpattern, error correcting information, etc., and the pit pattern isformed for the frame. In actual fact, accordingly, bit patternscorresponding to the respective channel bits of the synchronizingpattern and the error correcting information appear between the adjacentbit patterns corresponding to the data. The proportion of the affixedbit patterns, however, is only slight relative to the bit patterns ofthe data. In FIG. 3, therefore, it is assumed, for the brevity ofillustration, that each frame is constituted by only the pit patterncorresponding to the data. Pit patterns corresponding to the margin bitsstated before are also omitted from the illustration.

In the illustrated example, one of the interior and exterior of thecharacter/graphic pattern 14 is configured of the pit patterns each ofwhich corresponds to the data "89" and includes the pits 142 being 3Tlong, while the other is configured of the pit patterns each of whichcorresponds to the data "168" and includes the pit 143 being 11T long.Such an arrangement is based on the fact that, as explained before, thesmallest pit length and the greatest pit length are 3T and 11T in theEFM system, respectively, so the greatest difference of reflectances isexhibited between the pit patterns of the data "89" and the data "168".

The interior and exterior of the character/graphic pattern 14 may wellbe configured of two sorts of pit patterns different from the above,which correspond to the combination of other data and which realize thedifference of reflectances posing no problem in vision. It is alsoallowed that only one of the interior and exterior of thecharacter/graphic pattern 14 is configured of pit patterns correspondingto specified data, desirably, data whose pit patterns afford areflectance higher or lower than an average reflectance, while the otheris configured of a set of pit patterns corresponding to a set of randomdata. This contrivance is based on the fact that, since each pit ismicroscopic in vision, the set of pit patterns corresponding to the setof random data will exhibit a substantially averaged reflectance as thewhole set. Further, either of the interior or exterior of thecharacter/graphic pattern 14 may well be configured of pit patternswhich correspond to the combination of a plurality of sorts of specifieddata. Still further, both the interior and exterior of thecharacter/graphic pattern 14 may well be configured of pit patternswhich correspond to different combinations each consisting of aplurality of sorts of specified data.

In this manner, according to this embodiment, the character/graphicpattern 14 is formed by utilizing the pit patterns which correspond tothe data ordinarily used. Conversely, the formation of thecharacter/graphic pattern 14 can be effected similarly to the recordingof the ordinary data. Herein, however, the pit patterns constituting thecharacter/graphic pattern 14 need to be formed at a high positionalaccuracy. Accordingly, in the case of the example where the master discis formed with the pit patterns therefor by the laser while beingrotated by the disc motor, the positions of the pits to be formed arestrictly controlled to desired ones by the use of an encoder attached tothe disc motor, or any other measurement means.

In this way, the CD-ROM 4 formed with the character/graphic pattern 14can be produced in accordance with either of the CLV or CAV systems.

Now, let's consider a case where a CD-ROM of copy edition (an illegalcopy disc) is produced from the CD-ROM 4 thus formed with thecharacter/graphic pattern 14 by the CLV system.

As already defined before, the CD-ROM produced from the legal masterdisc shall be called the "original disc", and the illegal CD-ROMproduced by duplicating the original disc shall be called the "copydisc".

In the case of preparing the master disc of the original disc, themaster disc is formed with the pit patterns therefor in the above-statedway that the master disc is traced by the laser while being rotated bythe disc motor. On this occasion, subject to the CLV system for thepreparation of the master disc, the rotational velocity of the discmotor for rotating the master disc is controlled as explained below.

The rotational velocity which is stipulated by a predetermined referencefrequency is set for the disc motor. This rotational velocity iscontrolled so as to increase at a predetermined rate radially outwardsin order that a linear velocity at which the laser traces the masterdisc may be held constant. Simultaneously, the channel bits are read outone by one in accordance with a predetermined clock cycle, and writesignals for controlling the output power of the laser are generated onthe basis of the values of the channel bits. Thus, the pits are formedin succession.

In playing back the original disc, the rotational velocity thereof iscontrolled in order that the cycles of signals reproduced by an opticalpickup may be held constant. Herein, the channel bits and data aresuccessively restored on the basis of the values of the reproducedsignals read out by the optical pickup. Owing to the above control ofthe rotational velocity, the linear velocity of the original discincreases at a predetermined rate radially outwards.

Meanwhile, the preparation of the illegal master disc of the copy discproceeds similarly to that of the legal master disc of the originaldisc. The rotational velocity of a disc motor as is stipulated by apredetermined reference frequency is controlled in order that a linearvelocity at which a laser traces the master disc may be held constant.In this state, the channel bits reproduced from the original disc areread out one by one in accordance with a predetermined clock cycle, andwrite signals for controlling the output power of the laser aregenerated on the basis of the values of the channel bits. Thus, the pitsof the master disc are formed in succession.

Here, in order to prevent deviations or discrepancies of pit intervalsfrom developing between the copy disc and the original disc, it isessential that the relationship, in the preparation of the master discof the copy disc between, the linear velocity of the master disc beingtraced by the laser and the clock cycle for generating the writesignals, is in agreement with the relationship, in the preparation ofthe master disc of the original disc, between the linear velocity of themaster disc being traced by the laser and the clock cycle for generatingthe write signals.

However, granted that the clock cycles for generating the write signalsin the cases of preparing the master discs of the copy disc and theoriginal disc are in perfect agreement, the linear velocities in boththe cases cannot be brought into perfect agreement because of theproblems of the precisions of the reference frequencies and the rotationcontrols. Accordingly, the deviations of the pit intervals developbetween the copy disc and the original disc.

It is now supposed that the difference between the clock cycles forgenerating the write signals in the cases of preparing the master discsof the copy disc and the original disc is also calculated in terms ofthe difference between the linear velocities in the cases of preparingthese master discs. Under the supposition, the deviations of the pitintervals will be studied concerning the linear velocity in the playbackof the original disc and the difference between the linear velocities inthe cases of preparing the master discs of the copy disc and theoriginal disc.

FIG. 4B illustrates the positional relations of three tracks T₁, T₂ andT₃ which are successively adjacent on the CD-ROM shown in FIG. 4A. Inaddition, points A, B and C indicate pits which are respectively formedon the tracks T₁, T₂ and T₃. The pits A, B and C are aligned in thevertical direction as seen in FIG. 4B (in the radial direction of theCD-ROM), and they constitute the contour part of the character/graphicpattern.

Here, when the point A is set as a reference point by way of example,the points B and C of the original disc are relatively shifted to pointsB' and C' on the copy disc, respectively.

It is considered that the master disc of the copy disc is rotated arotational distance at a linear velocity v+Δv in a time period in whichthe master disc of the original disc performs one revolution at a linearvelocity v. The distance ΔL of the shift of the point B to the point B'corresponds to the magnitude of deviation of the rotational distance ofthe master disc of the copy disc from the revolution of the master discof the original disc. Therefore, the distance ΔL is given by Equation(1):

    ΔL=2 πR (Δv/v)                              (1)

where letter R denotes a radial length from the center of rotation ofthe disc to the track T₁.

In the CD-ROM, the inner radius R₁ of the record surface in which thedata are recorded is 25 mm!, and the outer radius R₂ thereof is 58 mm!.Therefore, the distance ΔL within the signal surface becomes:

    ΔL=(15.7 to 36.4)×10.sup.4 (Δv/v)  μm!(2)

Besides, the angle θ of a segment AB' relative to the rotating directionof the disc is given by:

    θ=tan.sup.-1 (P/ΔL)                            (3)

where letter P denotes the pitch of the tracks T₁ etc., which is 1.6 μm!in the CD-ROM.

Thus, assuming a tracking linear velocity deviation ratio (Δv/v) to be1×10⁻⁴, ΔL=15.7 to 36.4 μm! and θ=5.8 to 2.5 degrees! hold. That is,when the tracking linear velocity deviation ratio is on the order of10⁻⁴ (0.01 %!), the character/graphic pattern borne on the original disccomes to incline substantially horizontally on the copy disc. It is nextto impossible to identify such a horizontal character/graphic pattern.

Further, assuming the tracking linear velocity deviation ratio (Δv/v) tobe 1×10⁻⁵, θ=45.5 to 23.7 degrees! holds. Although the character/graphicpattern inclines, it is scarcely identifiable.

In view of the above calculations, in order to endow the copy disc withthe character/graphic pattern which is visible enough to be regarded asbeing identical to that of the original disc, the linear velocity of themaster disc of the copy disc must be controlled at a linear velocitydeviation ratio of 1×10⁻⁶ or below granted that the clock cycles forgenerating the write signals are in perfect agreement. In other words,even a very slight deviation in the linear velocity is greatlyinfluential to the extent that the character/graphic pattern etc.becomes unidentifiable.

It is technically very difficult, however, to control the linearvelocity at such a high precision during the preparation of the masterdisc of the copy disc. Moreover, since the clock cycles for generatingthe write signals do not actually agree perfectly, the linear velocityneeds to be controlled at a still higher precision when duplicating theoriginal disc.

By the way, in the standards of CD's for the CLV system including theCD-ROM, the tracking linear velocities are stipulated within acomparatively moderate range of 1.2 to 1.4 m/sec!. Therefore, a pirateintending to duplicate the original disc cannot know that the rotationalvelocity of the original disc in the playback and production thereofneed to be at the precision of or below 1×10⁻⁶ beforehand.

Accordingly, if the pirate intends to obtain a copy disc formed with thecharacter/graphic pattern favorably, he/she needs to prepare the masterdisc of the copy disc and find out the tracking linear velocity at whichthe character/graphic pattern appears, while changing the linearvelocity little by little at the precision of or below 1×10⁻⁶. Suchoperations, however, are almost impossible from the viewpoints oftechnical difficulty and job efficiency.

Furthermore, since the standard of the tracking linear velocity ismoderate as stated above, the fluctuation thereof within the stipulatedvalues poses no problem. In preparing the master disc of the originaldisc, therefore, random fluctuations may well be intentionally bestowedon the pit intervals within limits within which the fluctuation withinthe stipulated values arises in the linear velocity in the case wherethe rotational velocity is controlled so as to hold constant the cyclesof the signals reproduced from the original disc by the optical pickup.In this way, unless the fluctuation corresponding to the fluctuations ofthe pit intervals is bestowed on the linear velocity in the preparationof the master disc of the copy disc, the character/graphic patterncannot be formed favorably.

As thus far described, according to this embodiment, when the copy discof the CD-ROM (the CD-ROM of copy version) is produced using thereproduced signals derived from the original disc of the CD-ROM 4 (theCD-ROM of original version) of the CLV system bearing thecharacter/graphic pattern 14 thereon, the character/graphic pattern 14becomes distorted or nonexistent on the copy disc. As a result, if theCD-ROM is the illegal copy disc can be visually identified dependingupon the presence or absence of the exact character/graphic pattern 14,without the necessity of checking the played-back contents of theCD-ROM. Incidentally, it has heretofore been common practice to fastenthe label of a character/graphic pattern on the original disc or tocarve a character/graphic pattern in the original disc. Such acharacter/graphic pattern mechanically formed is very easy to duplicate.In contrast, the character/graphic pattern based on this embodiment isvery difficult to duplicate as stated before, because it is formed usingthe pit patterns of the signal surface.

Now, the second embodiment of the present invention will be described.

In this embodiment, an area for forming pits in accordance with the CAVsystem is especially provided in part of the original disc of a CD-ROMof the CLV system, and a character/graphic pattern is formed in the areaas explained before.

Data are recorded by the CLV system as usual in the area of the CD-ROMexcept the area for forming the character/graphic pattern therein. Here,when the copy disc of the CD-ROM is produced simply by the CLV system inorder to duplicate the data of the original disc, the character/graphicpattern formed on the original disc of the CLV system by the CAV systemis also duplicated by the CLV system. As a result, the character/graphicpattern recorded to be visible by the CAV system is drastically deformedto such an extent as to become invisible and seem nonexistent on thecopy disc by the change of a linear velocity, likewise to thecharacter/graphic pattern recorded on the CD-ROM of the foregoing firstembodiment. It is difficult for only the area of the original disc basedon the CAV system to be duplicated by the CAV system in order to producethe copy disc. The reason therefor is that the duplication is attendedwith the detection of the area of the original disc based on the CAVsystem, the detection of an angular velocity in the area based on theCAV system, and a rotation control and a write cycle control which aresuited to the detected contents. Thus, according to the secondembodiment, as in the foregoing first embodiment, whether or not theCD-ROM is the illegal copy disc can be visually identified dependingupon the presence or absence of the exact character/graphic pattern,without the necessity of checking the played-back contents of theCD-ROM.

FIG. 5 illustrates the relationship of the linear velocity of theoriginal disc in the second embodiment to the arrangement of the datarecording area of this original disc based on the CLV system and thecharacter/graphic pattern area thereof based on the CAV system. The axisof abscissas in the figure represents the distance (radius) R of thedisc measured from the center of rotation thereof, while the axis ofordinates represents the tracking linear velocity v at which a track atthe distance is traced.

Referring to FIG. 5, each part where the linear velocity v is constantis based on the CLV system, and each part where the linear velocity vincreases from the inner periphery of the disc toward the outerperiphery thereof is based on the CAV system.

As shown in the figure, a few methods are considered for inserting thepart of the CAV system into the area of the CLV system. With the methodwhich follows the parts CLV1-CAV1-CLV2 indicated by solid lines, the CLVarea and the CAV area can be joined without the gap of the linearvelocity. Therefore, the data can be recorded continuously and smoothlyeven at the boundary between both the areas. It is also facilitated toreproduce the data and to perform the rotational velocity control of thedisc.

In contrast, with the method which follows the parts CLV1-CAV2-CLV3 orCLV1-CAV3-CLV4 indicated by broken lines, the tracking linear velocity vdeviates or differs between the CLV area and the CAV area. Therefore,the rotational velocity of the disc needs to be rapidly changed at theboundary between both the areas. The same applies to the playbackoperation of the disc. Since, however, a great difference can be setbetween the tracking linear velocities of the CLV and CAV areas, thecharacter/graphic pattern can be reliably extinguished on the copy disc.Moreover, as will be described later, whether a disc is the originaldisc or the copy disc can be discriminated depending upon the presenceor absence of the CAV area in a playback system.

Contrariwise, a CD-ROM conforming to the CAV system may well be providedwith an area in which pit patterns are formed by the CLV system so as toform a character/graphic pattern therein. Thus, similar effects can bebrought forth.

Next, the third embodiment will be described.

In the third embodiment, a CD-ROM is provided with a plurality of areasfor forming character/graphic patterns in accordance with the CAV systemas shown in the second embodiment, and the angular velocities of therespective CAV areas are made different from one another. With thiscontrivance, the degree of difficulty copying is considerably increasedin the case where the copy disc of the CD-ROM having the same arealconfiguration as that of the original disc thereof is to be produced bydetecting the areas of the original disc based on the CAV system anddetecting the angular velocities of the areas based on the CAV system.Therefore, the effect of preventing the illegal duplication can befurther intensified.

FIGS. 6A thru 6C are diagrams each showing the relationship between thelayout of the plurality of CAV areas and the linear velocities thereof.

FIG. 6A illustrates a case where the plurality of CAV areas CAV4 andCAV5 are provided so as to be spaced in the radial direction of the disc4. The linear velocities of the individual CAV areas and the CLV area ofthe disc 4 are connected as indicated by the solid lines or broken linesin FIG. 5.

FIG. 6B illustrates a case where the plurality of CAV areas CAV6 thruCAV8 are provided so as to adjoin one another in the radial direction ofthe disc 4. By way of example, the linear velocities of the CAV areasCAV6 thru CAV8 and the CLV areas CLV5 and CLV6 of the disc 4 areconnected as indicated by solid lines or broken lines in FIG. 7.

FIG. 6C illustrates a case where the plurality of CAV areas CAV9 thruCAV11 are provided by partitioning an area of circular band shape in thecircumferential direction of the disc 4. By way of example, the linearvelocities of the CAV areas CAV9, CAV10 and CAV11 are connected asindicated by solid lines or broken lines in FIG. 8, so as to return tothe initial linear velocities every revolution of the disc 4.Incidentally, the lengths (angles) of the individual CAV areas need notalways be equal, and a CLV part can also be inserted between theadjacent CAV areas as occasion arises. Besides, in each of the examplesshown in FIGS. 6A and 6B, the angular velocities of the individual CAVareas need not differ from each other, but CAV areas of identicalangular velocity may well exist.

By the way, even in a case where the copy disc is produced by the CAVsystem from the original disc on which the character/graphic pattern isrecorded to be visible in accordance with the CAV system, thecharacter/graphic pattern becomes invisible on the copy disc unless itis duplicated at the same angular velocity as that of the original disc(at the deviation ratio of or below 1×10⁻⁶). Therefore, even when theillegal CD-ROM bearing the character/graphic pattern similarly to theoriginal disc is to be produced by detecting the position of each areaof the original disc based on the CAV system and the angular velocity ofeach area based on the CAV system, the same difficulty as in the firstembodiment is still involved.

Now, the fourth embodiment will be described.

In the fourth embodiment, an area for forming a character/graphicpattern in accordance with the CLV or CAV system is provided outside thedata area (program area) of a CD-ROM, and the data recording capacity ofthe CD-ROM is additionally reserved to that extent.

FIG. 9A is a sectional view showing the CD-ROM in this embodiment.

Referring to FIG. 9A, data are successively recorded from the positionof a program start diameter (φ50) toward the outer periphery of theCD-ROM 4 to, at most, a position which does not exceed the maximumprogram diameter (φ116). Accordingly, in a case where the data are ofsmall quantity, the outer diameter of the program area in which they arerecorded lies inside the maximum program diameter, and it is called an"outer program diameter". In addition, a so-called "lead-out area" inwhich data "0's" are recorded is provided outside the outer programdiameter.

Besides, a TOC (table of contents) area in which the index informationitems of the data stored in the program area are recorded is providedoutside a lead-in start diameter, and it is also called a "lead-inarea".

Usually, the inner side (22 in FIG. 9C) of the disc 4 with respect tothe lead-in area and the outer side (23 in FIG. 9B) with respect to thelead-out area are both made of specular portions. Since the specularareas 22 and 23 have no pits, the optical pickup of a playback systemcan perform neither a focusing operation nor a tracking operation inthese areas.

In this embodiment, the area for forming the character/graphic patternin accordance with the CLV or CAV system is provided on, at least,either of the inner side of the lead-in area or the outer side of thelead-out area.

In the case of providing the pattern forming area outside the lead-outarea, it is to be noted that, as seen from FIG. 9A, the outer side of alead-out diameter (φ117) is too narrow to bear the character/graphicpattern. In actuality, therefore, the outer program diameter may be setat φ111 (111 mm!) to provide the lead-out area inside the lead-outdiameter (φ117) anew, and the area for forming the character/graphicpattern may be provided outside the new lead-out area.

It is also allowed that the fine specular area (as shown at numeral 23in FIG. 9B) is provided outside the lead-out area, and that the area forforming the character/graphic pattern is provided outside the speculararea 23. Alternatively, it is also allowed that the fine specular area(as shown at numeral 22 in FIG. 9C) is provided inside the lead-in area,and that the area for forming the character/graphic pattern is providedinside the specular area 22.

A playback system in the prior art cannot perform a data readingoperation after jumping over the specular portion provided outside thelead-out area. Accordingly, when the specular portion (23 in FIG. 9B) isprovided, the data of the character/graphic pattern formed outside thisspecular portion are not read out. Consequently, the data of thecharacter/graphic pattern are not recorded on the copy disc. As will bedescribed later, therefore, whether the pertinent CD-ROM is the originaldisc or the copy disc can be identified in such a way that the presenceor absence of the character/graphic pattern is decided on the basis ofdata reproduced from the pattern forming area, in the playback operationof the CD-ROM in the playback system according to the present invention.

Now, the fifth embodiment will be described.

The fifth embodiment concerns the aforementioned playback system whichplays back the CD-ROM of the fourth embodiment.

FIG. 10 illustrates the circuit arrangement of the playback system inthe fifth embodiment.

Referring to the figure, a playback signal read out of the CD-ROM 4 byan optical pickup 3 is amplified and waveform-equalized by apreamplifier 6. The resulting signal is subjected to EFM(eight-to-fourteen modulation) demodulation by a CD digital signalprocessor 408, and the demodulated data are sent to a CD-ROM controller409. After correcting any error in the received data and restoring thecorrected data to the original data array, the CD-ROM controller 409sends the resulting data to a host system 410. Here, channel bitpatterns recorded on the CD-ROM 4 have been actually obtained bysubjecting scrambled data strings and error correction codes to the EFM.However, channel bit patterns for forming the character/graphic patternneed not always be created by scrambling data, but they may well becreated directly as the channel bit patterns which are to be recorded onthe CD-ROM 4. By the way, in a case where the character/graphic patternis to be formed by the pit patterns of channel bit patterns obtainedthrough the EFM of scrambled data strings and error correction codes,the original data strings are created in consideration of the contentsof the scrambling.

Here, the playback system of this embodiment is also available for a CDfor musical use. In the case of playing back the musical CD, the CD-ROMcontroller 409 supplies the restored data to a D/A (digital-to-analogconversion) circuit 411. The D/A circuit 411 converts the supplied datainto an analog signal, which is delivered as an output.

Besides, in compliance with an access command from the host system 410,the CD-ROM controller 409 controls the servo operation of a servocircuit 404 for a disc motor 11 and the movement operation of a pickupfeeder 406 for the optical pickup 3 through an access controller 405.Numeral 412 designates a rotational speed detector which will beexplained in detail later.

In such a playback system, the rotational servo control of the discmotor 11 is performed by the servo circuit 404 as stated below.

FIG. 11 illustrates the circuit arrangement of the rotational servo loopof the servo circuit 404.

A sync signal detector 5 extracts the sync signal explained before, fromthe playback signal amplified and waveform-equalized by the preamplifier6. An f-V (frequency-to-voltage) converter 7 converts the extracted syncsignal into a voltage which is proportional to the frequency of the syncsignal. A phase comparator 8 makes the phase comparison between thefrequency of the sync signal and the oscillation frequency (referencefrequency) of a crystal oscillator 9 and sends an adder circuit 10 anerror signal proportional to the phase shift between the sync signal andthe oscillation frequency, thereby correcting the output of the f-Vconverter 7. The output of the adder circuit 10 is amplifiedappropriately and is sent to the disc motor 11 so as to control therotational frequency thereof. Besides, the actual rotational speed ofthe disc motor 11 is detected by the rotational speed detector 412, andthe detected value of the rotational speed is sent to the CD-ROMcontroller 409. The rotational speed detector 412 can be implemented bya tacho-generator or encoder which is attached to the disc motor 11.

Owing to such a circuit arrangement, the disc motor 11 has itsrotational frequency controlled in order that the frequency of the syncsignal may be held constant. Here, if the frequency of the sync signalread out of the CAV area of the disc 4 falls within the pull-in range ofthe phase comparator 8, the rotational frequency of the disc motor 11can be controlled so as to hold the sync signal frequency constant,irrespective of whether the disc 4 conforms to the CLV system or the CAVsystem.

As a result, in the case of the CLV system, the rotational speed of thedisc motor 11 is controlled so as to lower from the inner periphery ofthe disc 4 toward the outer periphery thereof, whereby the linearvelocity of each track is held constant. Besides, in the case of the CAVsystem, the rotational speed of the disc motor 11 is controlled so as tobe constant at all times. Here, the angular velocity which is used inthe CAV system is set in consideration of the pull-in range of the phasecomparator 8 so that the playback system of this embodiment can alsoplay back the area provided in the CD-ROM of the CLV system and formedwith the character/graphic pattern by the CAV system in each of thesecond, third and fourth embodiments.

In producing the disc 4 of the fourth embodiment (FIGS. 9A˜9C),identification information indicating whether the disc 4 is the musicalCD or the CD-ROM is recorded as the TOC (table of contents) informationon this disc. Besides, a predetermined password indicating the regularor legal supplier or distributor of the CD-ROM is stored in an area(such as a system area) which is stipulated by the volume and filestructure of the CD-ROM for program JIS (Japanese Industrial Standard)information interchange (JIS X0606-1990, ISO 9660) as are recorded nextto the TOC information. The password may well be enciphered and thenstored.

On the other hand, the password used by the regular supplier of theCD-ROM 4 of the fourth embodiment, and information on the position ofthe character/graphic pattern bearing area of the CD-ROM 4 offered bythe regular supplier are stored beforehand in a memory which is includedin the CD-ROM controller 409 of the playback system. The positionalinformation indicates, for example, the distance of thecharacter/graphic pattern bearing area from the lead-out area.

In the case where the password is enciphered and then stored in theCD-ROM 4, the CD-ROM controller 409 is furnished with means fordeciphering the enciphered password.

The playback system of this embodiment shown in FIGS. 10 and 11 detectsthe presence or absence of the character/graphic pattern bearing areaprovided outside the lead-out area, thereby deciding whether the CD-ROM4 about to be played back is the legal original disc or the illegal copydisc. Incidentally, the character/graphic pattern may be formed byeither the CLV system or the CAV system.

FIGS. 12 and 13 illustrate a playback process which is performed by theplayback system.

When a new disc is mounted, the CD-ROM controller 409 of the playbacksystem executes a process as shown in FIG. 12.

At a step 502 subsequent to a step 501 at which the power of theplayback system is turned ON, the CD-ROM controller 409 reads out theTOC (table of contents) information of the pertinent disc to check thelead-out position. At a step 503, it decides whether the pertinent discis a musical CD or a CD-ROM. In the case of the musical CD, the CD-ROMcontroller 409 supplies reproduced data to the D/A circuit 411 so as toexecute a playback process for the musical CD at a step 508.

In the case of the CD-ROM, the flow of the process shifts to a step 504.At this step, the CD-ROM controller 409 searches for the password of thesupplier of the CD-ROM by reading the contents of an area (such as asystem area) stipulated by the volume and file structure of the CD-ROMfor program JIS information interchange (JIS X0606-1990, ISO 9660) asare recorded next to the TOC information. At a step 505, the CD-ROMcontroller 409 checks if the password searched for agrees with apassword stored in the memory of this controller 409. When the passwordsagree, the flow of the process shifts to a step 506 at which a dedicateddisc bit flag is set, whereupon the process is ended. On the other hand,when the passwords disagree at the step 505, the flow of the processshifts to a step 507 at which the dedicated bit flag is cleared,whereupon the process is ended.

When the process shown in FIG. 12 has ended, the CD-ROM controller 409subsequently executes a process shown in FIG. 13. However, in the casewhere it has been decided that the mounted disc is the musical CD, atthe step 503, the process shown in FIG. 13 is not executed.

This process is started at a step 601. At a step 602, the CD-ROMcontroller 409 decides if the dedicated disc bit flag is set. Oncondition that the flag is set, the flow of the process shifts to steps1701 et seq. In contrast, on condition that the flag is cleared, aprocess corresponding to the contents of the pertinent disc is executedin the same manner as in the prior art at a step 603. Alternatively, inthe case where the dedicated disc bit flag is cleared, that is, wherethe passwords do not agree, the disc can be made unavailable by anexpedient such as the ejection thereof.

At the step 1701, the CD-ROM controller 409 reads out thecharacter/graphic pattern bearing area of the disc with reference to theinformation on the position of this area as has been stored in theinternal memory beforehand. On this occasion, even when the speculararea exists inside the character/graphic pattern bearing area, thecontroller 409 is adapted to read out the pattern area beyond thespecular area. Further, at the step 1702, the CD-ROM controller 409decides whether or not data are existent in the character/graphicpattern bearing area. When the data exist, the pertinent disc isrecognized as a regular CD-ROM at the step 1703. Thereafter, the CD-ROMis played back, and playback data are sent to the host system 410 (step610).

On the other hand, in a case where the data do not exist in thecharacter/graphic pattern bearing area, the pertinent disc is recognizedas an irregular CD-ROM at the step 1705. Then, the irregular CD-ROM ismade unavailable (step 612) by presenting the display that the pertinentCD-ROM is a copy disc, by ejecting the pertinent CD-ROM or/and bysuspending the playback operation of the playback system. Owing to sucha process, the copy disc produced by fully duplicating the original discof the CD-ROM cannot be utilized by the playback system.

By the way, in an ordinary playback system, a readout operation is notperformed beyond the lead-out position found at the step 502 in FIG. 12.

Now, the sixth embodiment will be described.

The sixth embodiment concerns a playback system for playing back theCD-ROM of the second or third embodiment, or the CD-ROM which is formedwith the character/graphic pattern by the CAV system in the fourthembodiment.

That is, the sixth embodiment is directed toward the CD-ROM in which thecharacter/graphic pattern is formed by the CAV system.

The circuit arrangement of the playback system in this embodiment is thesame as that of the playback system in the fifth embodiment as shown inFIGS. 10 and 11. The sixth embodiment, however, features decidingwhether or not the character/graphic pattern is recorded by the CAVsystem. In general, it is difficult to produce a copy disc from anoriginal disc in which the CLV system and the CAV system are coexistent.In this embodiment, therefore, any disc is decided as the original discin a case where the character/graphic pattern is recorded by the CAVsystem.

For this purpose, when the process shown in FIG. 12 has ended, theCD-ROM controller 409 subsequently executes a process shown in FIG. 14,instead of the process shown in FIG. 13. However, in the case it hasbeen decided that where the mounted disc is the musical CD at the step503, the process shown in FIG. 14 is not executed.

This process is started at a step 601. At a step 602, the CD-ROMcontroller 409 decides if the dedicated disc bit flag is set. Oncondition that the flag is set, the flow of the process shifts to steps604 et seq. In contrast, on condition that the flag is cleared, aprocess corresponding to the contents of the pertinent disc is executedin the same manner as in the prior art at a step 603.

At the step 604, the CD-ROM controller 409 accesses a track m includedin the character/graphic pattern bearing area of the disc, withreference to the information on the position of this area as has beenstored in the internal memory beforehand. At the next step 605, theCD-ROM controller 409 detects the rotational speed of the disc duringthe read of the track m, through the rotational speed detector 412.

Incidentally, the rotational speed can also be detected by measuring atime period which is required for one revolution of the disc. This timeperiod is found by controlling the optical pickup 3 so as to jumpbackwards by one track (so as to continue the tracking of an identicaltrack) midway through one revolution, and then measuring a time intervalelapsed from the reproduction timing of a certain specified data patterntill the next reproduction timing thereof. In this case, a data patterncorresponding to the featuring part of the character/graphic pattern canbe employed as the specified data pattern. In the case where therotational speed is detected in this way, the data pattern of thefeaturing part should preferably be stored in the memory of the CD-ROMcontroller 409 within the playback system in association with the storedpassword of the disc.

Subsequently, any track n different from the track m is accessed withinthe character/graphic pattern bearing area at the step 606, and therotational speed of the disc during the read of the track E is similarlydetected at the step 607.

At the step 608, the rotational speeds of the tracks m and n arecompared. If they agree, the flow of the process proceeds to the step609 at which the pertinent disc is decided as the regular CD-ROM(original disc) formed with the character/graphic pattern by the CAVsystem. At the next step 610, the CD-ROM is played back, and reproduceddata is sent to the host system 410.

On the other hand, in a case where the rotational speeds of the tracks mand n disagree, the pertinent CD-ROM is made unavailable by presentingthe display that the pertinent CD-ROM is a copy disc, by ejecting thepertinent CD-ROM or/and by suspending the playback operation of theplayback system (steps 611 and 612). Owing to such a process, the copydisc produced by fully duplicating in accordance with the CLV system theoriginal disc which is formed with the character/graphic pattern by theCAV system cannot be utilized by the playback system.

In the above process, the tracks m and n should desirably be atpositions which are as far as possible from each other within the areaof the character/graphic pattern. The reason therefor is that theagreement or disagreement of the rotational speeds can be more reliablydecided.

Besides, the number of tracks to have their rotational speeds detectedmay well be set larger than two, so as to render the decision morereliably. By way of example, it is also allowed to detect the rotationalspeeds of all tracks included in the area of the character/graphicpattern and to find the agreement or disagreement of all the detectedrotational speeds.

Now, the seventh embodiment of the present invention will be described.

This embodiment concerns a playback system in which a copy disc isdecided on the basis of the values of data corresponding to theconstituent pit patterns of a character/graphic pattern.

The circuit arrangement of the playback system in this embodiment is thesame as that of the playback system in the fifth embodiment as shown inFIGS. 10 and 11. In the seventh embodiment, however, a data patternobtained by reproducing the character/graphic pattern bearing area of adisc is stored as a collating data pattern in the memory of the CD-ROMcontroller 409 beforehand. In addition, when the process shown in FIG.12 has ended, the CD-ROM controller 409 subsequently executes a processshown in FIG. 15, instead of the process shown in FIG. 13. However, inthe case where it has been decided that the mounted disc is the musicalCD at the step 503, the process shown in FIG. 15 is not executed.

The process shown in FIG. 15 is started at a step 701. At a step 702,the CD-ROM controller 409 decides if the dedicated disc bit flag is set.On condition that the flag is set, the flow of the process shifts tosteps 704 et seq. In contrast, on condition that the flag is cleared, aprocess corresponding to the contents of the pertinent disc is executedin the same manner as in the prior art at a step 703.

At the step 704, the CD-ROM controller 409 reads out the data of thecharacter/graphic pattern bearing area with reference to the informationon the position of this area as has been stored in the internal memorybeforehand. Subsequently, the collating data pattern stored in theinternal memory beforehand is read out at the step 705, and the patternof the data read out at the step 704 and the data pattern read out atthe step 705 are collated at the step 706. When the collation results inagreement, the pertinent disc is recognized as an original disc at thestep 707. At the next step 708, the CD-ROM is played back, and playbackdata are sent to the host system 410.

On the other hand, in a case where the collated patterns disagree, thepertinent CD-ROM is made unavailable by presenting the display that thepertinent CD-ROM is the copy disc, by ejecting the pertinent CD-ROMand/or by suspending the playback operation of the playback system(steps 709 and 710).

Owing to such a process, the copy disc being the CD-ROM which is formedwith the character/graphic pattern by an expedient such as printing, inorder to look like the original disc, can be made unavailable in theplayback system.

In the above process, the collating data pattern which is stored in thememory of the CD-ROM controller 409 beforehand need not always be set asthe whole data pattern obtained by reproducing the character/graphicpattern bearing area of the CD-ROM, but it may well consist of only adata pattern corresponding to a featuring part in the character/graphicpattern.

By way of example, only the data pattern corresponding to the featuringpart of the character/graphic pattern as shown in FIG. 16 may well bestored so as to collate it for the decision of the mounted disc.

In the example shown in FIG. 16, the data pattern corresponding to thefeature of the character/graphic pattern can be obtained by reading outonly the contents of tracks 801, 802 and 803.

Moreover, since the pattern of data for the whole circumferences of thetracks 801 to 803 is not required for the collation of the feature, onlythe sectors of these tracks corresponding to the featuring part of thecharacter/graphic pattern may well be read out and collated. Here, onesector is composed of a predetermined number of frames, and each sectoris endowed with a sector No. for identifying it. In this case, the trackNos. and sector Nos. of the tracks 801, 802 and 803 required foraccessing the sectors corresponding to the featuring part of thecharacter/graphic pattern are stored in the memory of the CD-ROMcontroller 409 beforehand.

Incidentally, the data pattern to be stored in the memory of the CD-ROMcontroller 409 beforehand may well be enciphered or encoded so as toreduce a necessary memory capacity.

In the above, the optical discs and the playback systems embodying thepresent invention have been described as to the cases where theinformation recording media are CD-ROM's.

However, the foregoing embodiments are not restricted to CD-ROM's, butthey are similarly applicable also to other information recording mediaon which information are recorded by affording optical features thereto,for example, CD's, minidiscs, optical discs and magnetooptic discs.Moreover, they are applicable even to non-disc type informationrecording media, for example, optical memory cards.

Here, applications to the optical memory cards will be exemplified.

FIGS. 17A thru 17D illustrate the principles of recording/reproductionsystems for the optical memory cards.

The recording/reproduction systems for the optical memory cards includea card rotation type shown in FIG. 17A, a head rotation type shown inFIG. 17B, a card reciprocation type shown in FIG. 17C, and a beam scantype shown in FIG. 17D.

The optical memory cards of the card rotation type and the head rotationtype are essentially the same as the CD-ROM's except for the differentshapes of the storage media. Accordingly, the foregoing embodiments canbe directly applied to these systems.

In addition, the optical memory cards of the card reciprocation type andthe beam scan type can be formed with character/graphic patterns whichare difficult to reproduce by duplication, in terms of pit patternscorresponding to data.

The embodiments of the present invention have been described above.

As thus far described, the embodiments of the present invention canrealize optical discs, such as CD-ROM's, which are formed with visiblecharacter/graphic patterns concerning trademarks and copyrights.

Moreover, when the copy disc of such an optical disc is produced fromthe original disc thereof, the character/graphic pattern becomesdistorted or invisible. That is, the copy disc is immediately identifiedby sight. Therefore, the effect of suppressing the illegal duplicationof the optical disc can be expected.

Further, the distortion or invisible part of the character/graphicpattern of the copy disc of the optical disc can be brought about bydividing an area for recording the character/graphic pattern. Stillfurther, the character/graphic pattern can be recorded without spoilingthe information recording capacity of the optical disc, in such a waythat the divisional parts thereof are respectively recorded in the outerperipheral portion of the information recording optical disc withrespect to the outer program diameter thereof and in the innerperipheral portion of the same with respect to the lead-in startdiameter thereof.

Furthermore, when a password is recorded on the optical disc, a playbacksystem identifies the copy disc on the basis of the password and theinformation of the character/graphic pattern area and makes this copydisc unavailable.

The playback system identifies the copy disc when the character/graphicpattern bearing area is not recorded by the CAV system, on the basis ofa tracking linear velocity, and it makes this copy disc unavailable.Also, it identifies the copy disc by checking data read out of thecharacter/graphic pattern bearing area, and it makes this copy discunavailable.

By the way, dedicated playback systems are usually used in the field ofCD-ROM publications of games, dictionaries etc. In this regard, when anyof the playback systems in the embodiments is applied to such adedicated playback system, an optical disc produced by illegalduplication cannot be utilized. The playback system of the embodiment istherefore expected to demonstrate the effect of suppressing theprevalence of illegal optical disc copies of a regular optical disc.

In addition, when similar character/graphic patterns are recorded onoptical memory cards of various types, the same effects as in the caseof the optical discs can be brought forth.

As described above, according to the present invention, it is possibleto offer an information recording medium whose master disc can beprepared by a manufacturing process similar to that of the prior art,and which is formed with a visible pattern that is very difficult toreproduce by duplication.

It is also possible to offer a playback system which refuses to utilizeany information recording medium produced by duplicating theaforementioned information recording medium of the present invention.

What is claimed is:
 1. A playback system for playing back an opticaldisc which has a record surface, and which records information in termsof pit patterns formed on a plurality of tracks of the record surfaceand corresponding to data to-be-recorded; said optical disccomprising:at least one area which is provided on said record surface,and in which at least one specified pit pattern is concentratedly formedin order that a visible size pattern is presented in a patterndisplaying area provided on said record surface; an average opticalreflectance of said at least one specified pit pattern differing fromthat of surroundings of said at least one area to a visually perceptibleextent, wherein said visible size pattern is visible on the basis of adifference between said average optical reflectances; said playbacksystem comprising:a memory for storing therein positional informationwhich specifies a position of said pattern displaying area of saidoptical disc; reproduction means for reproducing the data recorded onthe optical disc mounted on said playback system; control means forreproducing the data from a specified area specified by said positionalinformation stored in said memory; and reproduction inhibition means forsuspending subsequent playback of said mounted optical disc on conditionthat the reproduction of said data from said specified area as specifiedby said positional information has failed.
 2. A playback system forplaying back an optical disc which has a record surface, and whichrecords information in terms of pit patterns formed on a plurality oftracks of the record surface and corresponding to data to-be-recorded;said optical disc comprising:at least one area which is provided on saidrecord surface, and in which at least one specified pit pattern isconcentratedly formed in order that a visible size pattern is presentedin a pattern displaying area provided on said record surface; an averageoptical reflectance of said at least one specified pit pattern differingfrom that of surroundings of said at least one area to a visuallyperceptible extent, wherein said visible size pattern is visible on thebasis of a difference between said average optical reflectances; whereinsaid pit patterns formed in said pattern displaying area are formed inaccordance with a CAV (constant angular velocity) system in which arotational velocity of said optical disc is held constant, and the pitpatterns formed in any areas of said record surface except said patterndisplaying area are formed in accordance with a CLV (constant linearvelocity) system in which a tracking linear velocity of said tracks isheld constant; said playback systems comprising:rotation means forrotating the optical disc mounted on said playback system; an opticalpickup for tracking said tracks of said optical disc and detecting saidpit patterns formed on said tracks; rotation control means forcontrolling a rotational velocity of said rotation means so as to hold adetection frequency for said pit patterns constant; rotational velocitydetection means for detecting said rotational velocity of said rotationmeans; a memory for storing therein positional information whichspecifies a position of said pattern displaying area of said opticaldisc; access means for accessing at least two of the tracks on aspecified area of said record surface of said mounted optical disc, saidspecified area being specified by said positional information stored insaid memory; and reproduction inhibition means for deciding if said pitpatterns are formed in accordance with said CAV system in said specifiedarea, on the basis of the rotational velocities of said rotation meansduring the accesses to said at least two tracks as detected by saidrotational velocity detection means, and for suspending subsequentplayback of said mounted optical disc on condition that said pitpatterns are not formed in accordance with CAV.
 3. A playback system forplaying back an optical disc which has a record surface, and whichrecords information in terms of pit patterns formed on a plurality oftracks of the record surface and corresponding to data to-be-recorded;said optical disc comprising:at least one area which is provided on saidrecord surface, and in which at least one specified pit pattern isconcentratedly formed in order that a visible size pattern is presentedin a pattern displaying area provided on said record surface; an averageoptical reflectance of said at least one specified pit pattern differingfrom that of surroundings of said at least one area to a visuallyperceptible extent, wherein said visible size pattern is visible on thebasis of a difference between said average optical reflectances; saidplayback system comprising:a memory for storing therein positionalinformation which specifies a position of said pattern displaying areaof said optical disc, and predetermined data for collation; reproductionmeans for reproducing the data recorded on the optical disc mounted onsaid playback system; control means for reproducing the data from aspecified area of said record surface of said mounted optical discthrough said reproduction means, said specified area being specified bysaid positional information stored in said memory; and reproductioninhibition means for collating the reproduced data with the collatingdata stored in said memory, and for suspending subsequent playback ofsaid mounted optical disc on condition that the two data do not agree.4. A playback system as defined in claim 2, wherein:said memory stores apredetermined password for collation therein; and said reproductioninhibition means determines the suspension of the subsequent playback ofsaid mounted optical disc when a password stored in a predetermined areaof said mounted optical disc and reproduced therefrom does not agreewith the collating password stored in said memory.
 5. A playback systemas defined in claim 2, wherein:said memory stores a predeterminedpassword for collation therein; and said reproduction inhibition meansdetermines the suspension of the subsequent playback of said mountedoptical disc when a password stored in a predetermined area of saidmounted optical disc and reproduced therefrom does not agree with thecollating password stored in said memory.
 6. A playback system asdefined in claim 3, wherein:said memory stores a predetermined passwordfor collation therein; and said reproduction inhibition means determinesthe suspension of the subsequent playback of said mounted optical discwhen a password stored in a predetermined area of said mounted opticaldisc and reproduced therefrom does not agree with the collating passwordstored in said memory.
 7. A playback system according to claim 1,wherein said visible size pattern is one of a character pattern and agraphic pattern.
 8. A playback system according to claim 2, wherein saidvisible size pattern is one of a character pattern and a graphicpattern.
 9. A playback system according to claim 3, wherein said visiblesize pattern is one of a character pattern and a graphic pattern.